Executive Summary

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
IPCC. 5 Additionally, the calculated emissions and sinks in a given year for the United States are presented in a
common manner in line with the UNFCCC reporting guidelines for the reporting of inventories under this
international agreement. 6 The use of consistent methods to calculate emissions and sinks by all nations providing
their inventories to the UNFCCC ensures that these reports are comparable. In this regard, U.S. emissions and sinks
reported in this Inventory report are comparable to emissions and sinks reported by other countries. The report itself
follows this standardized format, and provides an explanation of the IPCC methods used to calculate emissions and
sinks, and the manner in which those calculations are conducted.
On October 30, 2009, the U.S. Environmental Protection Agency (EPA) published a rule for the mandatory
reporting of greenhouse gases from large greenhouse gas emissions sources in the United States. Implementation of
40 CFR Part 98 is referred to as the Greenhouse Gas Reporting Program (GHGRP). 40 CFR part 98 applies to direct
greenhouse gas emitters, fossil fuel suppliers, industrial gas suppliers, and facilities that inject carbon dioxide (CO 2)
underground for sequestration or other reasons. 7 Reporting is at the facility level, except for certain suppliers of
fossil fuels and industrial greenhouse gases. The GHGRP dataset and the data presented in this Inventory report are
complementary.
The GHGRP data set continues to be an important resource for the Inventory, providing not only annual emissions
information, but also other annual information, such as activity data and emissions factors that can improve and
refine national emission estimates and trends over time. GHGRP data also allow EPA to disaggregate national
inventory estimates in new ways that can highlight differences across regions and sub-categories of emissions, along
with enhancing application of QA/QC procedures and assessment of uncertainties.
EPA uses annual GHGRP data in a number of category estimates and continues to analyze the data on an annual
basis, as applicable, for further use to improve the national estimates presented in this Inventory consistent with
IPCC guidance. 8
23
24
25
26
27
28
29
30
31
32
33
34
35
36
ES.1 Background Information
Greenhouse gases trap heat and make the planet warmer. The most important greenhouse gases directly emitted by
humans include carbon dioxide (CO 2), methane (CH 4), nitrous oxide (N 2O), and several other fluorine-containing
halogenated substances. Although the direct greenhouse gases CO 2, CH 4, and N 2O occur naturally in the
atmosphere, human activities have changed their atmospheric concentrations. From the pre-industrial era (i.e.,
ending about 1750) to 2015, concentrations of these greenhouse gases have increased globally by 44, 162, and 21
percent, respectively (IPCC 2013 and NOAA/ESRL 2017). This annual report estimates the total national
greenhouse gas emissions and removals associated with human activities across the United States.
Global Warming Potentials
Gases in the atmosphere can contribute to climate change both directly and indirectly. Direct effects occur when the
gas itself absorbs radiation. Indirect radiative forcing occurs when chemical transformations of the substance
produce other greenhouse gases, when a gas influences the atmospheric lifetimes of other gases, and/or when a gas
affects atmospheric processes that alter the radiative balance of the earth (e.g., affect cloud formation or albedo). 9
5 See .
6 See .
7 See and .
8 See
9 Albedo is a measure of the Earth’s reflectivity, and is defined as the fraction of the total solar radiation incident on a body that
is reflected by it.
2 DRAFT Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2015